1. Field of the Invention
The present invention relates to a class of novel narcissistic valence tautomeric molecules that individually function as optoelectronic switching devices. More specifically, these intramolecular devices are polyene-linked bis-anthracenyl compounds that are optically active and bear a dichalcogenide carbamate ester on one terminal position and a dichalcogenide iminium salt on the other terminal position, to provide compounds that are capable of undergoing valence tautomerization between degenerate cationic tautomeric forms which are enantiomeric to each other. The present invention describes a class of optoelectronic compositions which can be resolved and arranged as molecular switching devices useful for application as chemical sensors or for the transmission, modulation, storage or processing of information.
2. Related Art
Chemical compounds that tautomerize between two degenerate structures are known as narcissistic compounds and their tautomerization a narcissistic reaction [L. Salem, Acc. Chem. Res., Vol. 4, pp. 322-328 (1971).] When such narcissistic compounds are asymmetric, narcissistic reaction results in intraconversion between enantiomeric forms of the molecule. In U.S. Pat. No. 5,237,067 (R. R. Schumaker, Aug. 17, 1993), there is described a particular subset of asymmetric narcissistic compounds useful as molecular switching devices, of Formula (1) below:
where X is S or Se; where R and R1 are alkyl, or alkyl that together form a ring of carbon atoms; and where An is the anion of a strong acid. The chiral Z element, which changes chirality on tautomerization, is preferably —CH—CH2— so that a preferred structure and its narcissistic reaction is illustrated below (Scheme 1, where R=H):

In further elaboration of this structure, a series of derivatives was prepared in which the R substituents were substituted by a variety of multi-cyclic aromatic compounds, for example, 9,9-fluorenyl, 9,9-xanthenyl, 9,9-anthraquinonyl [J. P. Parakka et al., Ann. N.Y. Acad. Sci., Vol. 1006, pp. 94-103 (2003) and references therein]. All of these new narcissistic compounds were shown to be thermally active chiroptical switches. One compound, namely a 9,9-[4,5-bis(dithiophenyl)-anthraquinonyl] derivative, was shown to be optically switchable in the solid state.
Scheme 1 illustrates the principle of coupling together on common atoms, a dithiocarbamate ring-closing and a dithioiminium ring-opening to result in an asymmetric narcissistic reaction.
A non-obvious extension of this principle would be the separation of the coupled ring-closing dithiocarbamate and the ring-opening dithioiminium reaction on two different anthracenyl ring systems that are conjugatively linked by π-bonds that pass through an asymmetric ring system that changes chirality during the narcissistic reaction. This novel design takes advantage of the unique property of the aromatic anthracene molecule to undergo addition across the 9,10 carbons (the central ring) of the molecule [see: J. March, Advanced Organic Chemistry, 3rd Edition, John Wiley & Sons, Inc., p. 40 (1985)]. In addition, this novel design permits the incorporation of the asymmetric central ring system of the molecule as a resolved (optically active) component whereas this is not feasible in the structure of Scheme 1.